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Significant Accounting Policies - Mutual Fund Administration Gross and Net Revenue (Detail) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Revenue from External Customer [Line Items] |  |  |  |
Revenue | $ 35,554,280 | $ 38,264,674 | $ 102,895,420 | $ 119,542,174
Administration revenue, gross |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | 5,491,424 | 6,129,695 | 16,247,752 | 19,550,947
Fund related expense |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Expenses | 3,605,495 | 3,707,104 | 10,563,585 | 11,537,907
Mutual fund administration revenue, net |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |
Revenue | $ 1,885,929 | $ 2,422,591 | $ 5,684,167 | $ 8,013,040

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